In carrying out an evaluation test of signal transmission property or the like of an electronic device such as a BGA (ball grid array) device, a contact holder, having contacts each connectable to each terminal of the electronic device, is used. In recent years, a frequency of a signal used in the electronic device becomes higher, as a processing speed of the electronic device becomes higher. Corresponding to such a high-speed signal, the contact holder is also required to transmit the high-speed signal.
In transmitting a signal (in particular, a high-speed signal), it is important to maintain a characteristic impedance of a transmission line for transmitting the signal at a desired value, throughout the transmission line. To this end, a metallic block structure, provided with a coaxial transmission line having predetermined characteristic impedance, has been proposed.
For example, Patent Literature 1 describes that “a dielectric layer 15 is disposed on the periphery of a contact probe 10 via a second metallic film 16, and a first metallic film 17 is disposed on an outer surface of dielectric layer 15. Due to this, a capacitor 18 is formed between second metallic film 16 (movable pins 11, 12) and first metallic film 17 (a metallic sleeve 9).”
Patent Literature 2 describes that “a contact probe 21 for transmitting a high-frequency signal has annular probe holders 31 fixed to two parts on the periphery of contact probe 21, and probe holders 31 are fitted into a through hole 3 so that probe holders are positioned at upper and lower part of a metallic block 2. Due to this, a hollow portion is defined between contact probe 21 and metallic block 2, and a coaxial transmission line, having contact probe 21 as an inner conductor and metallic block 2 as an outer conductor, is formed, which has desired characteristic impedance.”
Patent Literature 3 describes that “a substrate 21 has a front surface where an array of front side electrodes 22 are formed and a back surface where back side electrodes 23 connected to front side electrodes 22 are formed. On both surfaces of substrate 21, upper and lower guide plates 25 and 26 are positioned, wherein an anisotropically conductive adhesive sheet 27 is positioned between each surface of the substrate and each guide plate. Upper and lower guide plate 25 and 26 have through holes 28 and 29, where a coil-shaped contact 31 is positioned.”